There is a known conventional technology for virtualizing networks in order to flexibly implement a multi-tenant environment. For example, there is a known technology called a Virtual Extensible Local Area Network (VXLAN), in which a virtual machine encapsulates a packet that is exchanged with another virtual machine and then transfers the encapsulated packet via the Layer (L) 3 network.
FIG. 38 is a schematic diagram illustrating a VXLAN. A multi-tenant system 60 illustrated in FIG. 38 includes a server 61 and a server 67 that are connected via a layer 3 network 66. Furthermore, the server 61 operates a hypervisor 62, whereby it operates, in the hypervisor 62, virtual machines (VMs) 63 and 64 and a virtual tunnel end point (VTEP) 65 that is a tunnel termination point. Furthermore, the server 67 operates a hypervisor 68, whereby it operates, in the hypervisor 68, VMs 69 and 70 and a VTEP 71.
The VM 63, the VM 64, the VM 69, and the VM 70 are virtual machines that are used by tenants and to which a different 24-bit visual networking index (VNI) is allocated for each tenant. Furthermore, the VTEP 65 and the VTEP 71 each attach a header that includes a VNI to a packet that is output from each of the VMs 63, 64, 69, and 70, encapsulates the packet, and then transfer the packet via the layer 3 network 66.
In the example illustrated in FIG. 38, a VNI “22” is allocated to each of the VM 63 and the VM 69 and a VNI “34” is allocated to each of the VM 64 and the VM 70. If the VM 63 issues a packet addressed to the VM 69, the VTEP 65 attaches, to the packet, a VXLAN header that includes the VNI “22” allocated to the VM 63 and then encapsulates the packet.
Then, the VTEP 65 transmits the encapsulated packet to the server 67 via the layer 3 network 66. In contrast, the VTEP 71 deletes the VXLAN header from the received packet and then outputs the packet to the VM 69. Consequently, the multi-tenant system 60 implements packet communication via the layer 3 network 66.
Furthermore, there is a known technology in which a switch converts a packet transmitted by using a Virtual Local Area Network (VLAN) to a VXLAN. For example, FIG. 39 is a schematic diagram illustrating the conversion of a VXLAN performed at two switches. In the example illustrated in FIG. 39, the multi-tenant system 60 includes a switch 72, between the server 61 and the layer 3 network 66, that has a function of the VTEP 65. Furthermore, the multi-tenant system 60 includes a switch 73, between the server 67 and the layer 3 network 66, that has a function of the VTEP 71.
Furthermore, in the example illustrated in FIG. 39, a 12-bit identifier (ID) of the Virtual Local Area Network (VLAN) is allocated to each of the VM 63, the VM 64, the VM 69, and the VM 70. For example, a VLAN number “10” is allocated to each of the VM 63 and the VM 69 and a VLAN number “20” is allocated to each of the VM 64 and the VM 70.
Furthermore, the switches 72 and 73 store therein conversion information that is used to convert the VLAN numbers allocated to the VM 63, the VM 64, the VM 69, and the VM 70 to VNIs. Then, the switches 72 and 73 convert the VLAN numbers to the VNIs. For example, for each VM, the switches 72 and 73 store therein, in an associated manner, the VLAN number “10” and the VNI “22” and store therein, in an associated manner, the VLAN number “20” and the VNI “34”, respectively. If the VM 63 outputs a packet addressed to the VM 69, the switch 72 identifies the VNI “22” that is associated with the VLAN number “10” that is allocated to the VM 63.
Then, the switch 72 attaches a header that includes the VNI “22” to the packet that is output from the VM 63, encapsulates the packet, and transmits the packet to the switch 73 via the layer 3 network 66. In contrast, the switch 73 identifies the VLAN number “10” that is associated with the VNI “22” included in the header of the received packet. Then, the switch 73 deletes the header of the received packet and outputs the packet to the VM 69 whose VLAN number is “10”.
With regard to the conventional technologies, see Japanese Laid-open Patent Publication No. 2002-247089; Japanese Laid-open Patent Publication No. 2011-254378, and Japanese Laid-open Patent Publication No. 2008-227695, for example. Further, refer to “VXLAN: A Framework for Overlaying Virtualized Layer 2 Networks over Layer 3 Networks draft-mahalingam-dutt-dcops-vxlan-00.txt”, URL: http://tools.ietf.org/html/draft-mahalingam-dutt-dcops-vxlan-00#page-9, Last access on Dec. 21, 2012.
However, with the technology that performs conversion of VLANs and VXLANs, each switch uses the same conversion information, in which a VLAN number is associated with a VNI. Consequently, there is a problem in that the number of VNIs that can be used across the entire multi-tenant system is limited to the maximum number of VLANs.